IBM Adds Mainstream Flash Drives To Power Systems
August 22, 2018 Timothy Prickett Morgan
We tend to be focused on compute in the IT industry, and the CPUs get a lot of the glory. But the fastest CPU in the world doesn’t amount to anything without peripherals to keep it fed. That is why, of course, that the main frame was called that, after all. There were plenty of other frames surrounding it, making it into a system.
This holds as true for the Power Systems machines as much as any other machine, and whether or not they are running IBM i, too. The good news is that IBM does a fairly good job of mainstreaming important stuff for the systems, even if the peripherals are not quite as cutting edge as the AS/400 was back in its early days – advanced memory and disk drives, top process technologies, and innovative software are its hallmarks, after all.
In announcement letter 118-061, Big Blue announced that what it calls mainstream 2.5-inch flash SSDs are now available for both Power8 and Power9 iron. These mainstream products are, as IBM explained, referring to read heavy environments. As we all know, despite much technological wizardry, writing to flash does eventually kill it, so keeping the write rates down is a key to longevity except in devices that intentionally have a lot of latent capacity build in to cover for flash memory cells as they die off.
In any event, these new drives attach to SAS controllers, not NVM-Express ports, and they have a duty cycle of one drive write per day over the course of five years, which is not bad considering the amount of capacity they hold and the relative size of data at most IBM i shops, which measures in the tens to maybe hundreds of terabytes of capacity except in extreme cases. (We know shops that have disks and only hundreds of gigabytes of capacity, too.) For drives that are used to cache data as it changes in the system, there are write-intensive units that have three, four, or five drive writes per day, which means that they can write three, four, or five times the total capacity of the drive, every day for five years. This is a lot of writing.
The new flash SSDs come in 931 GB, 1.86 TB, 3.72 TB, or 7.45 TB capacities, which is pretty fat even by disk drive standards and not typically the capacity that IBM i shops would use. For online transaction processing workloads, consistent read and write times and a heavy duty cycle have been the name of the game for decades, so disk drives have worked well. But the I/O rates of flash are so high and the capacities so large that many shops could see a radical improvement in the transaction throughput of their workloads by shifting from disk to flash and foregoing what in the past would have been an inevitable CPU upgrade and possibly a memory upgrade. The trick is to know where you are bound and only spend money on that problem.
IBM is still recommending that these particular mainstream units be used only in heavy read environments, so if you are looking to build a blazingly fast OLTP machine, you might need a mix of flash and disk or a mix of different kinds of flash and some intelligent tiering software for them. If you want to push it, IBM has a tool called the SSD Mainstream Fuel Gauge that is available on IBM i, AIX, and Linux operating systems and that tells users how much of the write life is available on a drive. If the price is write, buy mainstream drives and wear them out.
The new flash drives were available on August 17, and can be used in the Power8 and Power9 systems themselves as well as in the EXP24SX expansion drawers. The one thing IBM did not do this time around, as it usually does, is supply list prices for these drives. The announcement letter did indicate that the price per gigabyte would be lower than flash drives it has sold in the past and for write-intensive units that also carry a premium. We will try to get our hands on pricing and update this as we can.
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